This invention pertains to the field of laser projection technology. More particularly, this invention pertains to laser target devices used to align laser projection devices with subject articles.
Laser projection technology provides means for accurately projecting illuminated lines and curves onto surfaces of subject articles using laser projection devices. The projection of lines and curves onto subject articles is useful for, among other things, locating where component parts are to be assembled to such subject articles without requiring scales or hard tooling and for validating the configuration of such subject articles as compared to their nominal design dimensions.
The procedure for using laser projection technology typically comprises the providing of a laser projection device and of a subject article onto which it is sought to display a laser projection. Prior to projecting a laser beam onto the subject article, the orientation of the laser projection device relative to the subject article is often determined by aligning the laser projection device with whatever tooling supports the subject article. Such alignment often involves aiming the laser beam emitted by the laser projection device at several (usually six) reflective targets that are attached to the tooling. The relative positional coordinates of each of these six reflective targets is imputed into the software that controls the laser projection device. Thus, by initially manually aligning the laser beam with four of the six reflective targets, and then using the software to automatically align the laser beam with the remaining two reflective targets, the orientation and position of the subject article relative to the laser projection device can be determined via the laser projection device's software.
With the alignment between the subject article and the laser projection device determined, the laser projection device can then be utilized to project illuminated lines and curves onto the surface of the subject article. Typically, the software of the laser projection device utilizes a computer aided design (CAD) model of the subject article and makes calculations based thereon to direct the laser beam of the laser projection device in the desired pattern.
The above-mentioned steps of aligning a laser projection device with a subject article is often facilitated by utilizing laser target devices that each comprise a reflective target mounted on a stem. The stem of such a laser target device is typically formed in a manner such that the stem comprises a necked-down shank that is dimensioned similar to the shank provided on a common construction ball device of the type often utilized in connection with typical tooling assembly jigs. Holes formed into the tooling jig assemblies are dimensioned to tightly hold such shanks and thereby allow the laser target devices and construction ball devices to be attached to tooling jig assemblies by simply inserting the shanks thereinto. Thus, during alignment, it is common practice to remove the construction ball devices from the tooling jig assemblies and to install laser target devices in their place. In so doing, the positional coordinates of the reflective targets relative to the subject article are identical to those of the construction balls. Thus, the coordinates of the construction balls with respect to the subject article, which presumably are already known, can be utilized by the software of the laser projection device for alignment purposes. Alternatively, if the subject article is not supported by tooling, the laser target devices can be positioned at various locations adjacent the subject article. However, using this approach often requires some form of accurate, and typically expensive, three-dimensional measuring system to determine the relative coordinates of the various laser target devices with respect to the subject article.
Although the above-mentioned methods of aligning laser projection devices with subject articles achieve desired results, they are not without disadvantages. For example, a minimum of six laser target devices is often needed to properly align most laser projection devices and, in cases where the subject article is supported by tooling, there may be an insufficient number of construction ball device holes on the tooling for the required number of targets. Moreover, the laser projection device must be able to reflect its laser beam directly to the reflective target of each laser target device and thus attention must be paid to the placement of the targets so as to avoid obscuring the line-of-sight to such targets by the tooling or by the subject article itself. If, on the other hand, no tooling is utilized, as previously mentioned, the positional coordinates of the selected laser target locations must first be determined using some other three-dimensional measuring system. Yet further, regardless of which of these methods is utilized, if the subject article is bumped or otherwise moved relative to the laser target devices, the laser beam projection will be inaccurately projected.